The invention relates to a light-emitting diode arrangement with a light-emitting diode that is light-transmissive in an axial direction, preferably for use in examining instruments for ophthalmic optics.
It is known from German Pat. Nos. 2,507,723 and 2,552,839 to utilize light-emitting diodes as the stimuli in perimetric eye examining instruments. Such instruments comprise, besides a plurality of stimuli lit up briefly in various groupings, one or selectively several targets as fixation points which are constantly lit up during the course of the examination.
It is an object of the invention to provide an arrangement usuable as a stimulus as well as in the form of a fixation target. In this connection, it is a prerequisite that the light-emitting diodes used as the stimuli exhibit a luminous density [luminance] which is, to a high degree, the same for all of the diodes; the light sources employed as fixation targets are to differ considerably in color and brightness from the stimuli.
Due to the two last-mentioned criteria, light-emitting diodes permitting a color switchover by electronic means are unsuitable for the purpose contemplated herein.
According to a preferred embodiment of the invention, the above-noted object can be attained by combining a light-emitting diode with an additional, switchable light source, the switchable light source penetrating the light-emitting diode from its rear face toward its light-emtting side.
The arrangement of this invention can be used not only in perimetric eye examining instruments, but also in all cases where an indicator light is to be lit up on an intermittently different color and brightness.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompany drawings which show, for purposes of illustration only a single embodiment in accordance with the present invention.